The present invention generally relates to motor-driven air blowers and, in a preferred embodiment thereof, more particularly relates to apparatus for operatively supporting a drive motor and an associated impeller wheel on the housing portion of an air blower.
Centrifugal blowers of the type, for example, used to operatively flow air through forced air heating furnaces typically comprise a blower housing having an inlet side wall through which a circular air inlet opening is formed. The inlet opening is positioned over an open side of a centrifugal blower impeller positioned within the housing coaxially with the inlet opening. An electric drive motor is coaxially disposed within the impeller and has a drive shaft operatively coupled to a central portion of a closed inner side wall thereof. The cylindrical housing of the motor defines with the circular edge of the inlet opening an annulus through which air is drawn into the interior of the impeller during operation of the motor.
The motor is conventionally supported on the blower housing inlet side wall by circumferentially spaced motor mount members extending across the inlet annulus and secured at their opposite ends to the motor housing and the blower housing inlet side wall. One common prior art motor mounting technique, as shown in U.S. Pat. No. 4,759,526 to Crawford et al, is to connect three or four circumferentially spaced support legs to the outer side of the motor housing using a circularly shaped connector typically referred to as a "belly band". Typically, from their connection points on the belly band, the support legs extend axially outwardly along the motor housing to the fan housing wall. Each of the legs then bends, at generally a ninety degree angle, radially outwardly across the blower housing inlet opening and has its outer end suitably secured to the outer side of the blower housing inlet side wall.
Various problems, limitations and disadvantages have heretofore been associated with this conventional blower motor mounting system with its right angle mounting legs. For example, the relatively heavy motor/blower wheel assembly supported by the legs creates substantial bending loads in the leg portions that extend radially outwardly from the motor to the fan housing, thereby tending to undesirably deflect the legs. In order to sufficiently reduce this bending deflection more material must be added to the legs, additional legs must be added, or both. This conventional design requirement results in a more expensive mounting system, can create an undesirable increase in air inflow restriction, and a generally more rigid overall mounting system. While the more rigid mounting system lessens the bending deflection of the motor support legs, it also increases the amount of operational vibration transmitted from the motor to the blower housing, thereby undesirably increasing the operating noise of the blower.
The mounting system must support the motor/impeller assembly under two distinct loading conditions--a shipping condition and an operating condition. Typically, a furnace is shipped with the axis of its blower motor in a horizontal orientation, and the shipping loads are primarily vertically directed in both upward and downward directions. Downward transient shipping loads combine with the weight of the motor/impeller assembly to impose substantial bending loads on the radially outwardly extending portions of the conventionally configured motor support legs described above, and can cause breakage of one or more of the legs if they are not made sufficiently thick and rigid to withstand the shipping loads.
Operating loads, on the other hand place a constant bending load on the legs from the weight of the motor/impeller assembly in addition to a torsional load on the legs due to the torque of the motor, particularly during motor start-up. Attempts to oversize and stiffen the motor support legs in order for them to withstand vertical shipping loads (i.e., under the first loading condition), as mentioned above, tends to undesirably increase the transmission of vibration from the motor/impeller assembly to the blower housing during motor operation (i.e., under the second loading condition), thereby correspondingly increasing the operating noise of the blower.
It can be readily seen from the foregoing that it would be desirable to provide an improved blower motor mounting system that eliminates or at least substantially reduces the above-mentioned problems, limitations and disadvantages heretofore associated with conventional mounting systems of the general type described above. It is accordingly an object of the present invention to provide such an improved blower motor mounting system.